Ethernet Fabric (VDX, CNA)

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Mel
Contributor
Posts: 63
Registered: ‎10-16-2010

FCoE Help

Dell has come out with a new blade switch for its m1000e chassis. It's what they call the Dell PowerConnect M8428-K, which is really an OEM'd Brocade switch. The M8428-K is a 10G CEE blade switch that has 16 internal downlink (server-facing) CEE ports, 8 CEE external ports for uplink to a top of rack FCF, like the B-8000 or the Nexus 5K, and 4 1/2/4/8GB native FC ports.

With this switch, one can use the CEE ports for FCoE pass-through. I am assuming that it does FIP snooping. I believe that is a requirement to being a FCoE forwarder. However, one can also leverage the FC ports and configure the switch as an FCF, where the de-encapsulation of the FC packet from the Ethernet frame and forwarding to the FC SAN can be done on the switch itself without having to worry about an FCF at the top of rack. I imagine Brocade came up with this for those environments that dont have an FCF at the top of rack - otherwise, I cant imagine why anyone would want to leverage the blade as a FCF. Not much convergence there.

All this having been said, can a hybrid approach be taken, in which the 8428-K's FCF capabilities can be used for some of the FC SAN traffic simultaneously with the top of rack FCF? Does that make sense? Can this even be done? What is the value in using 2 FCFs?

Or is it a zero-sum-game, where its either the blade acting as the FCF or the top of rack?

See attached diagram.

Thank you

Contributor
Posts: 21
Registered: ‎01-23-2011

Re: FCoE Help

Hi, when you have an FCF in the ToR and you want to connect to it through a blade server switch module such as the M8428-K, you have two connectivity options available to you:

1) VE_Port to VE_Port (FCoE ISL) connection.  I know Brocade doesn't currently support this; or

2) use a FIP Snooping Bridge (FSB) in the blade server.  I don't believe the M8428-K can operate in this mode either and here's why:

A) Based on the spec sheet available on dell.com (http://www.dell.com/downloads/global/products/pwcnt/en/dell-m8428-spec.pdf) only the internal server facing ports provide support for DCB and FCoE.  The external uplinks only claim support for DCB (no FCoE) and as a result, I don't believe the M8428-K can currently be used as a FIP Snooping Bridge.  That having been said, I could be reading into the product documentation too much...

B) If the M8428-K did support a FSB mode, you wouldn't be able to connect it to a Brocade FCF since each of the FCoE interfaces on the 8000 only supports a single FCoE login. 

You also raised a point about splitting your FCoE logins so some could use the FCF in the M8428-K and others use the FCF in the ToR.  While I think this is theoretically possible, I don't believe you could do this today.

It's important to point out that I'm basing most of this on what I know about the 8000 and I'm assuming that the M8428-K doesn't represent a quantum leap in technology.  Brocade folks will correct me if I'm wrong..

There are a number of Brocade FCoE topology examples available in the FCoE Tech Book (http://www.emc.com/collateral/hardware/technical-documentation/h6290-fibre-channel-over-ethernet-techbook.pdf) if you are interested.

Regards, Erik

Mel
Contributor
Posts: 63
Registered: ‎10-16-2010

Re: FCoE Help

Erik:

Thanks for the detailed answer and link. What you're saying is news to me.

So, if I understand you correctly, the 8428 cannot be used as an FCoE pass-through in conjunction with the B-8000? Are you saying then that the 8428 can only be deployed as an FCF?

Where did you get your information regarding your first point, namely that you need to create a VE to VE ISL and that Brocade doesn't support FCoE ISLs?

Brocade folks:

I really need someone from Brocade to clear this up ASAP.

Does the B-8000 indeed only support single FLOGI per 10G CEE port?

And does the 8428-K support FIP snooping such that it can be sued with the B-8000 FCF??

Calling Chip Copper...Calling Chip Copper, come in Chip Copper!

External Moderator
Posts: 4,857
Registered: ‎02-23-2004

Re: FCoE Help

The 8428 support both 10G and FCoE.

AFAIK, you can without a problem ISL the 8420 with B8000.

Message was edited: Sorry Typo 8424 and 8420 = 8428

TechHelp24
External Moderator
Posts: 4,857
Registered: ‎02-23-2004

Re: FCoE Help

Additional, i found this Info

End to End FCoE

Support for end-to-end FCoE is achieved via FC ISLs, allowing FCoE traffic to be carried across multiple FC ISL hops eventually terminating in FC or FCoE storage.

TechHelp24
Contributor
Posts: 21
Registered: ‎01-23-2011

Re: FCoE Help

Hi, no problem, just trying to avoid confusion..  In regards to your questions:

So, if I understand you correctly, the 8428 cannot be used as an FCoE pass-through in conjunction with the B-8000? Are you saying then that the 8428 can only be deployed as an FCF?

<ES>  Yes, I am saying that I believe the 8428 cannot be used as an FSB and if by some off chance they support this on the 8428, you cannot use it in conjunction with the 8000 due to the one FCoE login per FCoE interface rule.

Where did you get your information regarding your first point, namely that you need to create a VE to VE ISL and that Brocade doesn't support FCoE ISLs?

<ES> General product knowledge of the 8000 that I picked up while working with the 8000 in the lab.

Regards, Erik

Contributor
Posts: 21
Registered: ‎01-23-2011

Re: FCoE Help

I completely agree that you can connect the 8428 to the 8000 via FC ISLs (E_Port to E_Port).  It's the FCoE ISLs (VE_Port to VE_Port) that are not supported yet.  You can also put the 8428 into AG mode and connect to Brocade and other vendors FCFs.

External Moderator
Posts: 4,857
Registered: ‎02-23-2004

Re: FCoE Help

--->>> It's the FCoE ISLs (VE_Port to VE_Port) that are not supported yet.

I don't think this will be supported in the Future due only the Internal Port Support FCoE and not External Port.

Another restriction is, FCoE is a End to End Solution and I don't think the 8428 External Port can one Day support both Protocols 10G / DCB and FCoE due a Chipset Design.

Is my opinion.

TechHelp24
Mel
Contributor
Posts: 63
Registered: ‎10-16-2010

Re: FCoE Help

OK, so this is lousy.....

This means that Brocade does NOT have a multi-hop FCoE solution because all they have in their portfolio is one FCF - the 8000, and thats it. So why does Brocade claim that they are the first vendor in the industry to provide an "end-to-end" FCoE solution? The only end-to-end solution I see here is a direct attach topology, where the CNA will present itself as a VN port to the fabric and the FCF it is directly connected to will present a VF port to the fabric.

I would still want this verified and clarifed by Dr. Copper or Ahmad. These guys seem to be the FCoE gurus for Brocade.

Let me ask you guys the following question regarding theory of operation of FCoE, which is product agnostic.

So, let's say we DO have an FCoE pass-through switch sitting between an Enode's CNA and the FCoE port of an FCF. Although the FCoE pass through switch is invisible to the FC stacks on both ends, its existence does impact the manner in which the FC stack of the FCF will process the FC ULP traffic. Namely, this topology creates a new paradigm for FC because FC is a point-to-point based technology, but connecting an FCoE pass through device to an FCF presents to the FCF a point to multipoint (p2mp) construct, in which the traffic flows from multiple ENodes(lets say blade servers with CNAs) are aggregated and fed to the FCF FCoE port. So, the FCF FCoE port sees multiple endpoints (p2mp) that it cannot present to the FC stack as such.

The fix for that is to use FIP to create multiple logical point-to-point virtual FC links, using the concept of virtual FC interfaces. The triplet used to define these virtual FCoE links is the MAC address of  endpoint A, the MAC address of endpoint B, and the VLAN that they  communicate on. The FCF will then present to its FC stack a collection of  virtual point-to-point links, which the FC stack will understand and be able to process.

My question then is this: What is "endpoint A" and "endpoint B" in this scenario? My gut tells me that endpoint A is the CNA, endpoint B is the FCF's FCoE interface and they both will belong to the same VLAN. Is that the case? If so, why do we need a VE to VE link between the FCoE pass through switch's uplinks and the FCF's downlink? It seems that as long as the FCoE pass through can support FIP snooping, that logical construct (the virtual connection triplet) with the endpoints I just described should be possible.

Thoughts?

Contributor
Posts: 21
Registered: ‎01-23-2011

Re: FCoE Help

I believe the VDX might be the End to End FCoE solution Brocade has been referring to recently.  Just because one product in their portfolio provides an "End to End" FCoE solution, doesn't mean they all have to...

In regards to your product agnostic questions.  The fact that FCoE looks like FC to ENodes is due to the fact that FCoE always creates Point to Point links between all of the end points.  This is one of the fundamental building blocks of FCoE.  I do agree that the presence of a FIP Snooping Bridge presents challenges to the FC Protocol and have discussed this point extensively in the following blog post (http://brasstacksblog.typepad.com/brass-tacks/2010/11/fip-fip-snooping-bridges-and-fcfs-part-1-fip-the-fcoe-initialization-protocol.html).

Point to Multipoint "like" functionality is something that is being included in FC-BB-6 and even this is done through the creation of multiple Point to Point links.  For more information, look at the PT2PT and VN2VN proposals.

In regards to identifying the point to point link via MAC A, MAC B and the VLAN.  The problem actually gets a bit more complicated when you look at what happens when there are multiple fabrics and think about the impact this may have on things like fabric zoning.  An interesting presentation to review here is the one titled "WWPN persistence".

The purpose of the VE_Port is to allow FCF's to connect to other FCFs.  As a result, you wouldn't connect a FSB to an FCF via VE_Ports.  Again, most of this is covered in the above blog post.

Regards, Erik

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